Primer testing device



y 15, 1962 H. L. MULLER ET AL 3,034,335

PRIMER TESTING DEVICE Filed Jan. 2 1959 V I 2y FIG.2.

FIG.3.

HOLLIS L.III\\AIEEIIY%R' YBYJSQANLEY KENT aafi mke #W W ATTORNEYS UnitedStates Patent 3,034,335 PR TESTING DEVIQE Hollis L. Mulier, YorkSprings, and Stanley J. Kent,

Abington, Pa, assignors to the United States oi America as representedby the Secretary of the Army Filed Jan. 2, 1959, Ser. No. 784,826

1 Claim. (Cl. 73-35) (Granted under Title 3'5, US. Code (1952), see.266) The invention described herein may be manufactured and'used by orfor the Government for governmental purposes without the payment of anyroyalty thereon.

- This invention relates to devices for testing primers such as areutilized to detonate explosive charges, and more especially to a primertesting device which functions to test a primer under substantially thesame as those encountered in its use.

Heretofore primers have been tested by the drop test method. In thismethod, a mass is dropped from a certain height. This mass strikes afiring pin which, in turn, strikes the primer being tested. By changingthe mass or the height from which it is dropped, it is possible to varythe energy delivered to the primer. This method is adequate for testingprimers intended to be fired by a spring actuated firing pin. I

Where the primer is intended to be fired by gas pressure, however,altogether different conditions are encountered. In this case, thefiring pin is held in place by a shear pin until there has been appliedto it a gas pressure suificient to shear the shear pin. The firing pinthen travels under extremely high pressure until it strikes the primerwith a force greatly in excess of that imparted by a spring actuatedfiring pin, The conventional drop test method is therefore unsuitablefor testing primers intended to be fired by gas operated firing pins.

in accordance with the present invention, this d'ilficulty is avoided bythe provision of a primer testing device which establishes conditionssimilar to those under which the primer is put to actual use. Theinvention will be better understood from the following description whenconsidered in connection with the accompanying drawings and its scope isindicated by the appended claim.

Referring to the drawings:

FIG. 1 illustrates the invention as applied to a high energy primertesting device,

FIG. 2 illustrates a low energy primer tester, and

FIG. 3 illustrates a short cartridge container which permits theperformance of the tested primer to be determined by photographing theflash produced by it.

The primer testing device of FIG. 1 includes a barrel it) which isthreaded at both ends. Threaded onthe gas pressure inlet end of thisbarrel is a cap 11 and threaded on its gas pressure outlet end is acartridge retainer 12. The end cap 11 is internally threaded forconnection to a gas supply pipe or hose. The purpose of the cartridgecontainer 12 is to hold a cartridge (containing the primer to be tested)against a firing pin receiving head 13. This head 13 functions to stopthe firing pin at the end of its travel and has an opening through whicha protruded end of the firing pin extends and strikes the primer. Thisstopping of the firing pin means after it has performed its purpose offiring the primer.

The firing pin 14 is slidable in the barrel 16, is fixed to this barrelby a shear pin 15' and has a seal ring 16. The length of the firing pinprotrusion 17 depends on the amount of indentation required to be formedin the particular primer under test. The firing head end of the barrelit) is provided with tour vents 18 to permit escape of the air ahead ofthe moving firing pin.

By varying the length of the barrel 10, it is possible to vary theenergy with which the firing pin strikes the primer and by varying thelength'of the protrusion 17, the indentation of the primer is varied. Itis thus possible to change these two factors which most afiect theperformance of the primer.

When the length of the barrel is too short for the end cap 11 andcartridge retainer 12 to be threaded onto it, the short barrel retainer19 of FIG. 2' may be used. In this case, the firing pin is fixed to abarrel 2% which includes a firing pin receiving head 13 and is insertedinto the retainer 19 after which a cartridge retainer similar tocartridge retainer 12 of FIG. 1 is threaded onto the retm'ner 19.

In preparing to test a primer in the device of FIG. 1, a barrel ofpredetermined length and a firing pin having a predetermined protrusionare selected after which the firing pin is fixed to the barrel by ashear pin as illustrated. Then the primer to be tested is inserted intoa cartridge, the cartridge is placed in the cartridge retainer 12, thefiring pin receiving head 13 is positioned at the end of the barrel andthe cartridge retainer is screwed onto the barrel. The end cap 11 isthen screwed onto the other end of the barrel and the gas supply pipe orhose is screwed into the end cap.

The actual test of the primer is consummated by admitting gas underpressure through the end cap connection. This ruptures the shear pin anddrives the firing pin against the primer with a force similar to that tobe encountered by this particular type of primer in actual use.

If it is desired to make a photographic record of the performance of thetested primer, a short cartridge retainer 21 (see FIG. 3) may be used.As will be understood by those skilled in the art, the preparation for atest with the device of PEG. 2 is similar to that outlined in connectionwith the device of FIG. 1. A purpose of the longitudinal slots 22 shownin the drawing in the cartridge case retainer 12 in FIG. 1, is to enablethe primer flame alone to be visible. Were a propellant present theissuing flame would be much longer and any photographic record of theflame would no longer be that of the primer being tested. An advantageof the head 13 is to absorb the energy of the firing pin 14 after it hasperformed its function of firing the primer being tested. In this way itmay preclude the protrusion 17 going further than necessary into aprimer cup and reduce the danger of excess gas pressure supplied to thecap 11 puncturing the cup of the primer being tested and allowing theprimer fiame to issue rearwardly as well as forwardly under reducedpressure and an error in the photographic record of the primer flamelength.

We claim:

A testing device for primers actuated by gas pressure in which thelength of a primer flame may be measured for the gas pressure used foractuating such primer, said device comprising in combination a barrelprovided at one end with connection for a source of gas pressure and atthe opposite end with a retainer for holding a primer being tested whilea primer flame may be visible, said connection including a cap threadedonto the outside of said barrel and having an internally threadedpassageway leading into said'barrel, said retainer for a primer beingtested being threaded onto an end of said barrel opposite said cap, afiring pin having a cylindrical main body with a cylindrical protrusionfixed on the forward end and of smaller diameter than the main body'andslidable in said barrel to fire a primer, a shear pin between saidbarrel and firing pin adjacent said cap, a firing pin receiving headbetween said retainer and said barrel and adapted to be pressed againstan end .of said barrel by said retainer, said head iirniting thepenetration of said firing pin intosaid primer and absorb the energy ofthe firing pin after it has fired a primer, and a vent passageway frominside the barrel adjacent said head to the outside of said barrel.

References Cited in the file of this patent UNITED STATES PATENTS

